AMASTRA, MOLOKAI. 253 



are traces of a very thin, brown, outer cuticle. The specimen 

 described above and figured is n'ot quite adult, judging by the 

 very thin outer lip. Length 9, diam. 5, aperture 4.1 mm.; 

 51/2 whorls. A shell in coll. U. S. Nat. Mus. is almost ex- 

 actly similar. 



This species is certainly very close to A. morticina of West 

 Maui, but in that the whorls are perceptibly shorter, the stria- 

 tion a little more distinct, and the suture crenulated. The 

 upper part of the spire in A. umbilicata and A. morticina 

 tapers more than in A. similaris. 



Section AMASTRELLA (p. 151). 



Series of A. petricola. 



Small forms with finely striate embryonic whorls; later 

 stages streaked or banded, without zigzag lines or fine mot- 

 tled pattern. 



The apical sculpture is not unlike that of the biplicata 

 group, of Lanai. The other 'characters of the shell point to 

 Amastrella as most nearly akin. 



66. A. PETRICOLA (Newcomb). PI. 36, figs. 4, 5. 



' Shell dextral, acutely conical, longitudinally coarsely 

 striate; whorls 6, rounded, sometimes the last one inflated; 

 suture simple, well impressed ; aperture rounded ovate ; lip 

 acute, slightly thickened within; columella rather long, with 

 a sub-central revolving plait ; often with an umbilicus ; color 

 dark corneous, outer and columellar lips margined exter- 

 nally with white or yellowish- white " (Newc.). 



Length 5, diam. 2 inch. (Newc.). 



Molokai : on the rocky sides of a pali or precipice (New- 

 oomb ) . Map alehu ( B aldwin ) . 



Achatinella petricola NEWC., Ann. Lye. Nat. Hist, of N. Y., 

 vi, 1855, p. 143; P. Z. S., 1855, p. 208; Amer. Jour, of 

 Conch., ii, p. 211. PFR., Monogr., iv, 558. Amastra petri- 

 color BALDWIN, Catalogue, p. 9. A. petricola SYKES, Fauna 

 Hawaiiensis, p. 341 (exclusive of Achatinella umbilicata 

 Pfr.). BORCHERDING, Zoologica, xix, p. 122, but not pi. 10, 

 f. 22, from Kamalo. 



